The invention relates to an apparatus for and method of monitoring a machine. The invention is well suited to the monitoring of wear in such machines as gearboxes but can also be applied to other mechanical systems in which rotating parts are present. As used herein the term xe2x80x9crotatingxe2x80x9d is intended to encompass any machine whose operation is cyclic in nature and thus includes among other things reciprocating machines.
In International Patent Application No. PCT/GB 91/02112 published as WO 92/09886, the teachings of which are incorporated herein by reference, there is described a system for monitoring debris in a fluid. The system comprises at least one electrostatic sensor for producing a signal representing electrostatic charge associated with the fluid moving past the sensor and with debris and/or impurities carried by the fluid. The signal from the sensor is conditioned by a signal conditioner and the conditioned signal is processed by a signal processor together with another signal representing at least the charge associated with the moving fluid in order to produce a signal representing the electrostatic charge associated with the debris and/or impurities. In practice two electrostatic sensors are used at spaced apart locations and the signals therefrom are processed, i.e. correlated, in order to identify the existence of debris in the moving fluid. The system is extremely useful for detecting wear in machines because machine wear causes charge carrying particles to be generated which can be detected by the system.
In International Patent Application No. PCT/GB 96/01407 published as WO 97/01093, the teachings of which are incorporated herein by reference, there is described an apparatus for monitoring a lubricant in a machine. The apparatus comprises electrostatic sensors for producing signals representing electrostatic activity in a machine lubricant and a temperature sensor for producing a signal representative of the temperature of the lubricant. A signal processor is arranged to compensate for temperature related changes to the signals from the electrostatic sensors in response to the signal from the temperature sensor, and to process the signals from the electrostatic sensors to detect an electrostatic activity precursor that is indicative of an impending wear event in the machine.
The present invention resides in the discovery that there is a change in electrostatic activity in a machine at the location of a part whose operation is cyclic, for example a rotating or reciprocating part, when that part is experiencing an abnormal loading.
In one aspect the invention provides an apparatus for monitoring a machine, the apparatus comprising a sensor for producing a signal representing electrostatic activity in the vicinity of plural interacting components of the machine, a tacho generator for generating a tacho signal representing a cycle of the machine, and a signal processor for processing the signal from the sensor together with the tacho signal to monitor for abnormal conditions in the interaction between the plural components.
In another aspect the invention provides a method of monitoring a machine, the method comprising producing a signal representing electrostatic activity in the vicinity of plural interacting components of the machine, generating a tacho signal representing a cycle of the machine, and processing the signal together with the tacho signal to monitor for abnormal conditions in the interaction between the plural components.
In another aspect the invention provides a method of and system for monitoring operation of a machine by detecting cyclic electrostatic activity at interacting components of the machine indicative of an abnormal loading or wear thereat.
In another aspect the invention provides a method of and system for monitoring a machine lubricating fluid, in which method and an electrostatic signal is processed depending on a cycle of the machine to identify machine cycle dependent electrostatic activity at a selected location within the machine.
An ability to detect such a change in electrostatic activity enables potential problems with the running of a machine to be identified before a failure occurs in the machine. Thus, wear or even catastrophic failure in a machine may be avoided as a result of the advance warning enabled by the invention.
The above and further features of the invention are set forth with particularity in the appended claims and together with advantages thereof will become clearer from consideration of an exemplary embodiment of the invention given with reference to the accompanying drawings in which: